JPH06201743A - Rotor position detecting device - Google Patents

Abstract

PURPOSE:To decrease influence of noise to enhance position detection accuracy of a rotor by providing a high-pass filter for eliminating a low frequency component in a front stage side of a wave detector. CONSTITUTION:When eddy current sensors 4a, 4b are excited by a high frequency power source 5 while a rotor 1 is being rotated, an eddy current is generated on a surface of the rotor 1 and impedance of the sensors 4a, 4b are changed in accordance with the eddy current. The impedance of the sensors 4a, 4b caused by the generated eddy current is detected as divided voltage, a low frequency noise signal caused by leakage flux and the like is eliminated by high-pass filters 7a, 7b, and then wave detection is performed by detectors 8a, 8b so that relative positions between the sensors 4a, 4b and the rotor 1 can be detected. Position detection signals outputted from the sensors 4a, 4b are fed to an electromagnet control circuit to selectively excite respective paired electromagnets so that the rotor 1 can be moved in the direction for correcting positional displacement and therefore the rotor 1 can be positioned with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating body position detecting device, and more specifically, it is preferably applied to a rotating body represented by a motor which is supported by a magnetic bearing or the like in a non-contact manner. The present invention relates to a body position detecting device.

[0002]

2. Description of the Related Art Conventionally, in order to support a motor or the like that rotates at an extremely high speed, magnetic bearings have been adopted with a focus on the advantage that frictional resistance can be prevented from occurring between a rotating body and a bearing. Here, the magnetic bearing is, for example, at least a pair of electromagnets at a target position with a rotating body made of a magnetic body interposed therebetween.
Generally, two pairs of electromagnets are arranged, each pair of electromagnets is alternately excited to generate an attractive force to the rotating body, and the rotating body is moved to the electromagnet side where the attractive force is generated. Is. And, by shortening the period for alternately exciting the electromagnets of each pair as much as possible, equivalently obtaining a state in which the attraction force by the electromagnets of each pair acts on the rotating body,
Achieving a sufficiently strong rotating body holding force.

Further, when the rotating body is located near the center of each pair of electromagnets, the rotating body can be positioned and supported with high precision by exciting the electromagnets as described above. When a certain amount of displacement occurs, the above displacement can be eliminated by continuing to excite only one of the electromagnets of each pair. As is clear from the above description, when a magnetic bearing is used, it is necessary to detect the position of the rotating body with high accuracy in a non-contact manner. Expression sensors have been proposed.

The eddy current sensor detects a change in impedance due to an eddy current generated on the surface of the rotating body when the rotating body is excited at a high frequency. This is for detecting the change in the formed inductance, and any of the sensors can detect the position of the rotating body in a non-contact manner and with considerably high accuracy. Specifically, for example, when an inductance type sensor is used, a high frequency voltage is applied to each pair of coils via a resistor or the like, and the voltage at both ends of the coils is detected to detect the position displacement signal of the rotating body. Then, it has been proposed to detect the position of the rotating body based on this position displacement signal (see Japanese Patent Laid-Open No. 63-21519).

[0005]

When any of the above-mentioned sensors is used, the position displacement signal obtained by detection contains noise due to leakage magnetic flux and the frequency of the position displacement signal. And the frequency of the noise are not so different from each other, a highly accurate position displacement signal cannot be obtained. Further, in order to remove the noise signal, it is possible to interpose a low-pass filter or the like in the subsequent stage of the detection circuit, but since there is no significant difference between the position detection signal frequency after detection and the noise frequency, there is no sufficient noise. Cannot be reduced, and thus the accuracy of detecting the position of the rotating body cannot be improved so much.

Since the high frequency voltage applied to the coil is amplitude-modulated, it is easily affected by external noise, and the position displacement signal is generated in the same manner as noise caused by leakage magnetic flux. Since the frequency is not so different from the frequency of 1, the noise cannot be reduced sufficiently even by interposing a low-pass filter or the like, and the position detection accuracy of the rotating body cannot be improved so much.

As described above, since the accuracy of detecting the position of the rotating body cannot be improved so much, the position of the rotating body rotated at an ultrahigh speed such as a turbo molecular pump cannot be controlled very accurately. There is a risk that the rotating body such as the turbo molecular pump will be displaced by more than the limit amount and eventually the turbo molecular pump will be damaged.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a rotating body position detecting device capable of significantly reducing the influence of noise and increasing the position detecting accuracy of a rotating body. It is an object.

[0009]

In order to achieve the above object, the rotating body position detecting apparatus according to the first aspect is provided with a filter means for removing at least a low frequency component in front of the detecting means. In the rotating body position detecting device according to the second aspect, the excitation frequency of the sensor is set to be high so that the level of the noise component does not affect the displacement detection signal.

According to another aspect of the present invention, the rotating body position detecting device further includes an inverter for rotationally driving the rotating body, and the carrier frequency of the inverter is set high so that the noise component level does not affect the displacement detection signal. It is set. The rotating body position detecting device according to claim 4 further comprises an inverter that rotationally drives the rotating body, and the switching speed of the inverter is set to be slow so that the level of the noise component does not affect the displacement detection signal. There is.

[0011]

According to the rotating body position detecting device of the present invention, a sensor for generating a predetermined impedance or inductance by applying a predetermined excitation frequency is arranged at a predetermined position with respect to the rotating body. When the output signal is detected by the detecting means to obtain the impedance change or the inductance change of the sensor and the relative position displacement of the rotating body is detected based on the impedance change or the inductance change, the filter means provided in the preceding stage of the detecting means Since at least the low frequency component is removed by this, it is possible to significantly reduce the noise component included in the detection output, and as a result, it is possible to improve the position detection accuracy of the rotating body. Specifically, the frequency of the noise component due to the leakage magnetic flux is remarkably lower than the predetermined excitation frequency, so that the noise component can be easily removed by interposing the filter means in front of the detection means. As a result, the accuracy of detecting the position of the rotating body can be improved.

According to the rotating body position detecting device of claim 2,
Since the predetermined excitation frequency is set high,
The effect of removing noise components by the filter means can be enhanced, and the accuracy of detecting the position of the rotating body can be further enhanced. According to the rotating body position detecting device of claim 3, since the carrier frequency of the inverter is set to be high so that the level of the noise component does not affect the displacement detection signal, in addition to the function of claim 1, A given excitation frequency, for example, without being significantly affected by noise signals,
It becomes possible to set the frequency at which the detection sensitivity becomes high.

According to the rotating body position detecting device of claim 4,
Since the switching speed of the inverter is set so slow that the noise component level does not affect the displacement detection signal, the level of the noise component itself can be sufficiently attenuated. The detection accuracy can be improved.

[0014]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 1 is a block diagram schematically showing an embodiment of a rotating body position detecting device of the present invention. Two pairs of electromagnets (not shown) are set with a rotor 1 made of a magnetic body as an example of the rotating body as a reference. And an electromagnet control circuit (not shown) that selectively supplies an excitation signal to each pair of electromagnets. In addition, two pairs of eddy current sensors 4a and 4b (however, in FIG.
Is shown in FIG. 1), and a resistor 4 is provided between the terminals of the common high frequency power source 5 respectively.
eddy current sensors 4a, 4 when connected in series with c, 4d
b is connected. In FIG. 1, 6a, 6b and 6c are stator windings, and 6 is for supplying a multi-phase AC power source whose phase is deviated by a predetermined electrical angle to the stator windings 6a, 6b and 6c. Inverter.

The eddy current sensors 4a and 4b and the resistor 4
The divided voltage at the connection point with c and 4d is supplied to the detectors 8a and 8b via the high-pass filters 7a and 7b, and the signal of the frequency component near the power supply frequency of the high frequency power supply 5 is used as the position detection signal for the electromagnet control circuit. Is being supplied to. The operation of the rotating body positioning device having the above configuration is as follows.

By exciting the eddy current sensors 4a and 4b by the high frequency power source 5 while the rotor 1 is rotating, eddy currents are generated on the surface of the rotating shaft 1, and the eddy current sensors 4a and 4b correspond to the eddy currents. The impedance of 4b changes. Therefore, the impedances of the eddy current sensors 4a and 4b caused by the generated eddy currents are detected as the divided voltage and detected by the wave detectors 8a and 8b, whereby the relative positions of the eddy current sensors 4a and 4b and the rotating shaft 1 are detected. Can be detected. Then, the position detection signal output from the eddy current sensor 4 is supplied to the electromagnet control circuit, and the electromagnet control circuit selectively excites each pair of electromagnets to move the rotary shaft 1 in a direction to correct the position displacement. The rotary shaft 1 can be positioned with high accuracy.

Although the above description is based on the assumption that there is no low-frequency noise due to leakage magnetic flux or the like, in general, such low-frequency noise does not exist at all.
Therefore, for example, when it is affected by the noise signal shown in FIG. 2A, the inter-terminal signal of the eddy commutation sensor 4a is affected by the noise signal as shown in FIG. If this inter-terminal signal is detected by the wave detector 8a, a position detection signal greatly affected by the noise signal can be obtained as shown in FIG. 2 (C). Even if the electromagnet is controlled by the electromagnet control circuit based on this position detection signal, the rotor 1 cannot be accurately positioned. However, in this embodiment, since the high-pass filters 7a and 7b are provided in front of the respective detectors 8a and 8b, the detectors 8a and 8b detect the low-frequency noise signals caused by the leakage magnetic flux. As a result, highly accurate position detection can be achieved. More specifically, the frequency spectrum of the noise signal due to the leakage magnetic flux and the position detection signal detected by the eddy current sensors 4a and 4b is as shown in FIG. Since there is a difference, the noise signals can be removed with high accuracy by the high-pass filters 7a and 7b, and the position detection signals hardly affected by the noise signals can be obtained by the wave detectors 8a and 8b.

FIG. 4 is a frequency spectrum showing a state in which the noise signal is removed by the high-pass filters 7a and 7b. A considerable noise signal remains in the intermediate frequency band, but this residual noise signal is detected after detection. It can be almost completely removed by passing it through a low-pass filter. Further, as is clear from the above description, by setting the power supply frequency of the high frequency power supply 5 higher, the noise signal removing effect of the high pass filters 7a and 7b can be remarkably enhanced, and the position detection accuracy can be remarkably enhanced. it can.

In the above embodiments, the high-pass filters 7a and 7b are used to remove low frequency noise signals.
However, it goes without saying that a bandpass filter that selects only frequency components near the power supply frequency of the high frequency power supply 5 may be used. Further, in the above description, the noise signal caused by the inverter 6 or the like is not considered at all, but the noise signal caused by the inverter or the like is, as shown in FIG. Therefore, the noise signal removing effect can be similarly enhanced by setting the power supply frequency of the high frequency power supply 5 to be high. On the contrary, when the switching circuit such as the inverter 6 is viewed as a noise generation source, if the waveform is blunted by slowing the switching speed, as shown in FIG. 5B, the signal level of the noise signal is attenuated. Is substantially equivalent to that when the power supply frequency of the high frequency power supply 5 is set high, and the noise removal effect can be enhanced. Further, the same effect can be achieved even when the carrier frequency of the inverter 6 is set high. In this case, since the noise signal removal is achieved by setting the carrier frequency, the power supply frequency of the high frequency power supply 5 can be appropriately set.
The position detection sensitivity can be increased by setting the frequency at which the detection sensitivity becomes high. Further, in order to further reduce the high frequency component generated from the inverter 6, for example,
It is conceivable to increase the gate drive resistance of the switching element, add a snubber circuit between the drain and source terminals of the switching element, or connect an impedance several times the leakage impedance to the connection point of a pair of switching elements. .

Furthermore, an electromagnet which is a noise signal source,
The frequency components of the noise signal caused by the electromagnet control circuit, the eddy current sensors 4a and 4b, the detection circuit for the eddy current sensor, the inverter circuit, various power supply circuits, etc. are detected in advance,
By providing the bandpass filter corresponding to the frequency band in which the position displacement signal can be detected without being affected by the noise signal, it is possible to prevent the circuit configuration from becoming complicated by providing the filter for each noise signal source. of course,
The frequency of each of the various noise signal sources may be set to a frequency largely separated from the frequency band of the position displacement signal, and in this case, the power supply frequency of the high frequency power supply 5 can be set to a frequency at which the detection sensitivity becomes high. Therefore, the position detection sensitivity can be improved.

FIG. 6 is an electric circuit diagram showing a main part of still another configuration example of the present invention.
An inductor 11 is connected between the emitter terminals, a capacitor 12 is connected between the base and collector terminals, and an eddy current sensor 4a is connected between the collector and emitter terminals to form a Hartley oscillator circuit. Here, the inductance of the inductance 11 and the inductance of the eddy current sensor 4a are L2 and L1, respectively,
When the capacitance of the capacitor 12 is C1, the oscillation frequency F is F = 1 / [2π {(L1 + L2) C1} ^1/2 ]. Since L2 and C1 are constants, the oscillation frequency F becomes a function of the inductance L1, and as shown in FIG. 7, the oscillation frequency F and the inductance L1 are 1: 1.
Will be taken.

Therefore, the position detection signal can be obtained by converting the oscillation frequency obtained by the above oscillation circuit into an amplitude component by using a conversion circuit similar to a conventionally known FM receiver. In this case, since the frequency is modulated by the change in the inductance of the eddy current sensor 4a, it is possible to obtain a highly accurate position detection signal with high noise resistance.

Although the oscillation frequency is changed by changing the impedance of the eddy current sensor in this embodiment, it is needless to say that the oscillation frequency can be changed by changing the inductance of the capacitance type sensor.

[0024]

As described above, according to the first aspect of the present invention, at least the low frequency component is removed by the filter means provided on the upstream side of the detection means. Therefore, there is a unique effect that the accuracy of detecting the position of the rotating body can be improved.

The invention of claim 2 has a unique effect that the effect of removing the noise component by the filter means can be enhanced, and the accuracy of detecting the position of the rotating body can be further enhanced. In addition to the effect of claim 1, the invention of claim 3 has a unique effect that the predetermined excitation frequency can be set to a frequency at which the detection sensitivity becomes high without being significantly affected by the noise signal. Play.

The invention according to claim 4 has a unique effect that the level of the noise component itself can be sufficiently attenuated, and in turn, the position detection accuracy of the rotating body can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a rotary body positioning device incorporating an embodiment of a rotary position detecting device of the present invention.

FIG. 2 is a diagram illustrating the influence of a noise signal on a position displacement signal after detection.

FIG. 3 is a diagram showing frequency spectra of a position displacement signal and a noise signal caused by leakage magnetic flux and the like.

FIG. 4 is a diagram showing a frequency spectrum in the preceding stage of the detector.

FIG. 5 is a diagram showing a frequency spectrum of a position displacement signal and a noise signal caused by an inverter or the like.

FIG. 6 is an electric circuit diagram showing a main part of still another configuration example of the present invention.

7 is a diagram showing the relationship between the oscillation frequency and the impedance of the eddy current sensor in the configuration example of FIG.

[Explanation of symbols]

 1 Rotor as a rotating body 4 Eddy current sensor 5 High frequency power supply 6 Inverter 7a, 7b High-pass filter 8a, 8b Detector

Front page continuation (72) Inventor Fumitaka Kimura 2 at 1000 Otani, Okamoto Town, Kusatsu City, Shiga Daikin Industry Co., Ltd. Shiga Factory (72) Inventor Kashin Oyama 2 at 1000 Otani, Okamoto Town, Kusatsu City, Shiga Prefecture Industrial Co., Ltd. Shiga Works

Claims (4)

[Claims] 1. Sensors (4a) (4b) which generate a predetermined impedance or inductance when a power source of a predetermined excitation frequency is applied are arranged at predetermined positions with respect to the rotating body (1), and the sensors (4a ) The output signal from (4b) is detected by the detection means (8a) (8b) to obtain the impedance change or the inductance change of the sensors (4a) (4b), and the rotating body is based on the obtained impedance change or the inductance change. The rotary body position detecting device for detecting relative position displacement of (1) is characterized in that filter means (7a) (7b) for removing at least low frequency components is provided in front of the detection means (8a) (8b). And a rotating body position detecting device. 2. The rotating body position detecting device according to claim 1, wherein the predetermined excitation frequency is set high so that the level of the noise component does not affect the displacement detection signal. 3. An inverter (6) further comprising an inverter (6) for rotationally driving the rotating body (1).
2. The rotating body position detecting device according to claim 1, wherein the carrier frequency is set to be high so that the level of the noise component does not affect the displacement detection signal. 4. An inverter (6) further having an inverter (6) for rotationally driving the rotating body (1).
The rotation speed of the rotating body position detecting device is set so that the noise component level does not affect the displacement detection signal.